The present invention relates to a load elevator and, more particularly, to a truck lift that is stowable in an out-of-the-way position when not in use as a load elevator.
A truck lift (commonly referred to as a lift gate), typically comprises a load platform connected to a hydraulically powered mechanism for raising and lowering the platform between ground level and the bed of the truck. In the so-called conventional lift gate, the platform is pivotally connected to the raising and lowering mechanism and, in the transit position, occupies a vertically disposed and elevated position closing the tailgate opening of the truck bed. Thus, when a driver wishes to back up to a loading dock for purposes of loading directly onto the truck bed, he must first get out of the vehicle and operate the conventional lift gate in a mode to move the platform out of the tailgate position. This disadvantage is inherent in conventional lift gates, whether of the type in which the powered mechanism for raising and lowering the platform comprises a parallelogram linkage system or a pair of runner assemblies that are vertically reciprocable with respect to guide channels or rails.
In the case of conventional lift gates mounted on parallelogram linkage systems, the foregoing disadvantage has been overcome by the so-called fold-under lift gate wherein the load platform is invertible with respect to the lifting linkages and thus can be raised to an out-of-the-way position beneath the bed of the truck. However, a disadvantage remains in the foldunder lift gate in that the platform, whether of one piece or two piece construction, is relatively heavy and only manually movable into and out of the inverted position. In the case of the rail type conventional lift gate, the disadvantage of manual manipulation of the platform is eliminated in that the platform can be gravitationally lowered to a dockloading position while remaining vertically disposed but, nevertheless, the driver must still leave the cab of the vehicle in order to accomplish the lowering to the dockloading position.
U.S. Pat. No. 3,795,329 discloses a rail-type lift gate having a foldable two piece platform which is locked in the folded configuration in a transit and dockloading position, i.e., such that the upper edges of the two platform sections do not protrude above the level of the floor or bed of the vehicle. In this device the frame of the lift gate includes a pair of opposite side rearwardly projecting brackets or flanges formed with upwardly directed slots adapted to receive latch pins on opposite sides of the outer platform section. However, the two piece platform must be manually restrained into the collapsed condition during vertical movement of the collapsed platform and its latch pins into and out of the slots of the brackets or flanges of the framework of the device. Once the platform sections are lowered into place, the platform cannot be directly unfolded out of the collapsed condition but must first be elevated to lift the latch pins out of the slots. Furthermore, the construction is of a type such that when the platform in the dockloading position it does not provide an upper surface that is substantially continuous and flush with the bed of the vehicle.